口(くち)が滑(すべ)る

くちがすべる
expression
to let something slip; to say something one shouldn't have
idiomcommunication
1. to let something slip; to blurt out a secret by accident
To say something one meant to keep quiet, without intending to. Literally 'one's mouth slips.' Almost always used in the past tense as an admission or an excuse, and typically about a secret or an unflattering remark.
つい口(くち)が滑(すべ)った。
It just slipped out.
口(くち)が滑(すべ)って秘密(ひみつ)を話(はな)してしまった。
I let it slip and told them the secret.
酒(さけ)が入(はい)ると口(くち)が滑(すべ)りやすくなるから気(き)をつけよう。
You let things slip more easily once you've had a drink, so be careful.
誕生日(たんじょうび)のサプライズだったのに、弟(おとうと)の口(くち)が滑(すべ)って台無(だいな)しになった。
It was supposed to be a birthday surprise, but my little brother let it slip and ruined it.

Structure: 口(くち) (mouth) + が + 滑(すべ)る (to slip).

Common patterns

  • つい口(くち)が滑(すべ)る: to let it slip without thinking
  • 口(くち)が滑(すべ)って…言(い)ってしまう: to blurt out ~ by mistake
  • 口(くち)が滑(すべ)りやすい: to be prone to letting things slip

Similar words

Usage

Because it frames the words as accidental, the phrase works as a softened apology: 口(くち)が滑(すべ)りました, 'that came out wrong.'

Related Words

Compare: 口(くち)が軽(かる)い (unable to keep a secret)
Compare: 口(くち)を滑(すべ)らせる (to let slip)
Compare: 口(くち)が堅(かた)い (tight-lipped, discreet)
general
Added 2026.8.12 12:18 · Revised 2026.9.2 13:02
30500/30585_kuchigasuberu